Spring applied, fluid pressure released brake

ABSTRACT

A disc brake for heavy machinery such as metal working presses and the like which includes a rotatable disc mounted on a projecting shaft for rotation with the shaft and for axial movement relative to the shaft. A stationary brake ring is mounted on the frame of the machine and has a face adjacent to one side of the disc. The other side of the disc faces an axially movable brake ring which is locked to the stationary brake ring to prevent relative rotation therebetween. A cover plate is fixed to the stationary brake ring. Springs are provided between the cover plate and the axially movable brake ring to bias the brake against the disc to thereby apply braking pressure to the shaft and fluid motor means are provided to overcome the bias of the springs to thereby release the brake. Shims are provided between the cover plate and the stationary brake ring so that, as the braking surfaces wear, the initial spring tension may be reestablished by removing one or more shims.

United States Patent [72] Inventor Walter J. Grombka FOREIGN PATENTS l N333 2 934.142 8/1963 Great Britain l88/l 70 l A {g g 0 Sept 24, 1968Primary ExaminerDuane A. Reger 45] Patented Feb 2, I971Attorney-McNenny, Farrington, Peame and Gordon [73] Assignee TheNational Machinery Company Tiifin, Ohio 8 co po ati 0f Ohio ABSTRACT: Adisc brake for heavy machinery such as metal working presses and thelike which includes a rotatable disc mounted on a projecting shaft forrotation with the shaft and [54] APPLIED FLUID PRESSURE RELEASED foraxial movement relative to the shaft. A stationary brake 26 6 D ring ismounted on the frame of the machine and has a face adrawmg jacent to oneside of the disc. The other side of the disc faces [52] U.S. Cl 188/170, an axially movable brake ring which is locked to the stationary188/723, 188/196 brake ring to prevent relative rotation therebetween. Acover [51 Int. Cl ..F16d 65/24, plate is fixed to the stationary brakering. Springs are provided Fl6d 55/ l 6 between the cover plate and theaxially movable brake ring to [50] Field of Search 188/72, bias thebrake against the disc to thereby apply braking pres- I 170, 196V, 264Asure to the shaft and fluid motor means-are provided to overcome thebias of the springs to thereby release the brake. [56] References CltedShims are provided between the cover plate and the stationary UNITEDSTATES PATENTS brake ring so that, as the braking surfaces wear, theinitial 2,914,142 11/1959 Klaue 188/72 p g tension y be reestablished yremoving one or mere 3,082,647 3/1963 Banker 188/ l 70X Shims- I l s 12e PATENTEDFEB 2|97l i 3559772 sum 1 or 3 MCA/C'A/W MWRMMIO annals/MomATV RA/EKL SPRING APPLIED, FLUID PRESSURE RELEASED BRAKE BACKGROUND OFTHE INVENTION This invention relates to disc brakes for heavy machinerysuch as metal working presses and the like, wherein the machine operatesthrough one complete cycle for forging one piece and then comes to restupon the disengagement of a clutch and the application of a brake. Whilethe machine is at rest, the operator removes the forged article andinserts another blank into the dies after which the machine is recycled.It is highly important in such single-cycle forging machines that themachine may be brought to rest with the dies in a predetermined openposition to permit insertion of the blank between the dies. Since suchbrakes must be designed to withstand high inertia loads when applied, itis necessary to provide brakes which transfer braking torque directly tothe machine housing without applying substantial torque to brakeapplying linkages to minimize shear forces on such linkages.

Such prior art brakes usually comprise disc-type brakes having arotatable member mounted for rotation on the crankshaft of the forgingmachine. The rotatable member has an annular brake section which isgripped between a stationary brake ring mounted on the machine frame anda movable brake ring which is axially movable relative to the stationarybrake ring. The movable brake ring is moved into braking contact withthe annular brake section by fluid-operated piston means and is releasedtherefrom by springs, e.g. US. Pat. No. 2,778,451 to R6. Friedman, or ismoved into contact with the annular brake section by springs and isreleased from the brake section by fluid-operated piston means, e.g. US.Pat. No. 2,775,319 to R.G. Friedman. According to the disclosure of thelatter patent, the brake application force exerted by the springs may beadjusted to compensate for brake lining wear by adjusting exposedlocknuts holding the springs. Such an adjusting operation may be,however, improperly performed by the machine operator, since it isimpossible for him to determine or gauge the proper, as installed,spring force which is applied to the annular brake section. The operatormay adjust the spring tension so that undue wear is imposed on the brakelinings, causing premature failure of such linings. Furthermore, he maytighten the springs to such an extent that the fluid-operated piston maynot function to fully disengage the movable brake ring from the annularbrake section, thus causing an undesirable drag on the brake liningsduring machine cycling.

Since considerable heat is generated between the rotating brake sectionand the brake applying member, it is highly desirable to cool theannular brake section. Prior art brake assemblies include channeling inthe brake applying members through which a coolant is circulated. Suchchanneling involves cutting and boring operations which increase thecost of the brake and provide passageways which may become scaled andcorroded if demineralized water or special coolants are not employed.

Many existing brake assemblies have brake applying and brake releasingdevices which act on a movable brake ring. Since considerable force mustbe applied by the brake releasing device to overcome the brake applyingpressure exerted by the brake applying member and since such brakeapplying and brake release members are usually radially spaced aconsiderable distance apart, the movable brake ring in such prior artdevices becomes deflected and even permanently warped by the forcesapplied thereto. Such deflection results in uneven application of thebrake and undue wear of the brake lining.

A brake produced in accordance with the teachings of this inventionovercomes many of the problems set forth above and includes a rotatablemember mounted on the crankshaft of a cyclically operated formingmachine for rotation with the shaft but axially movable relative to theshaft. A stationary brake ring is mounted on the machine frame betweenthe frame and the brake member and has a face adjacent to one side of anannular section of the rotatable brake member. An axially movable brakering is provided adjacent to the other side of the annular brake sectionand locking means are provided between the stationary brake ring and theaxially mova ble brake ring to prevent relative rotation therebetween. Acover plate is fixed to the stationary brake ring and, with thestationary brake ring, defines an annular chamber within which theannular brake section and the axially movable brake ring are located.Springs are provided between the cover plate and the axially movablebrake ring to bias the brake ring against the annular brake section toapply the brake to the shaft and fluid-operated piston means areprovided to overcome the bias of the springs to release the brakes.Since the springs are provided between the cover plate and the axiallymovable brake ring, the operator cannot tamper with the springs tochange their settings. However, the biasing force of the springs may bereestablished if reduced by wear between the brake applying members andthe annular brake section. According to this invention such anadjustment is performed by removing one or more shims which are providedbetween the cover plate and the stationary brake ring. By a simplegauging technique, the machine operator may determine how many shims toremove in order to establish initial spring tension. The removal of oneor more shims, moreover, establishes uniform spring pressure about thecircumference of the movable brake ring to prevent the unevenapplication of spring pressure to the movable brake ring.

According to another aspect of this invention, the fluidoperated pistonmeans for releasing the brake includes an annular pressure chamber inthe fixed brake .ring and a plurality of brake applying pins extendingfrom an annular piston mounted in the annular pressure chamber and intopressure applying contact with the movable brake ring. Shims areprovided between the pins and the movable brake ring so that theeffective length of the pins may be reduced as shims are removed betweenthe stationary brake ring and the cover plate.

According to a further aspect of this invention, the locking meansbetween the stationary brake ring and the movable brake rings includes aplurality of radially extending slots in the stationary brake ring and acorresponding plurality of radial projections on the movable brake ringwhich cooperate with the slots. Replaceable side check plates may beprovided on the radial projections so that they may be replaced if worn.

According to a still further aspect of this invention, the annular brakesection is cooled by air passageways which extend radially through thestationary brake ring and into the braking chamber.

OBJECTS or THE INVENTION In view of the foregoing, it should beappreciated that it is an important object of this invention to providea disc brake for a cyclically operated forming machine which hastamperproof springs which may be adjusted to compensate for brake wearby a simple operation.

It is a further object of this invention to provide a disc brake for acyclically operated forming machine wherein braking torque istransferred from the brake applying members directly to the machinehousing and wherein torque pressure receiving members are replaceable ifworn.

It is a still further object of this invention to provide a disc brakefor a cyclically operated fonning machine wherein air coolingpassageways are provided into a braking chamber.

It is a still further aspect of this invention to provide a disc brakefor a cyclically operated forming machine wherein the brake applyingforce is exerted in alignment with and substantially unifonnly along thebraking surfaces to reduce bending moments on the movable brake memberand to provide a uniform distribution of the braking force.

According to a still further aspect of this invention, the distancebetween the center of spring applied force and the center of brakereleasing force is minimized to correspondingly minimize deflection ofthe movable brake ring.

These and other objects, features. and advantages of the invention willbecome more apparent and more readily understood from the followingdetailed description of the preferred embodiment and from theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation showing a brakeaccording to this invention applied to a forging press;

FIG. 2 is a fragmentary perspective view of a quadrant of the stationarybrake ring;

FIG. 3 is an enlarged fragmentary elevational view of the brakeaccording to this invention with a portion of the cover plate brokenaway and showing the stationary and movable brake rings in section toshow a certain detail of construction;

FIG. 4 is a cross-sectional view, the plane of the section beingindicated by the line 4-4 in FIG. 3;

FIG. 5 is a cross-sectional view, the plane of the section beingindicated by the line 5-5 in FIG. 3; and

FIG. 6 is a cross-sectional view, the plane of the section beingindicated by the line 6-6 of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to thedrawings, a bed frame 10 of a forging press having a crankshaft 11projecting therefrom is illustrated. It is characteristic of forgingpresses that they operate in a cyclic fashion, that is, each revolutionof the crankshaft 11 effects a forging operation, and that the machineis brought to rest after each forging operation. The accuracy and theefficiency of the braking operation is frequently a measure of theeffectiveness of the forging machine. In order to provide such a brakingfunction, a disc brake assembly 12 is provided on the forging machine.To support the brake assembly 12, four spaced feet or lugs 14 arecarried by the bed frame 10 and the braking torque is transmitted to thebed frame 10 by the feet or lugs 14.

The crankshaft 11 has keyed to it a hub 15 which is provided with anannular flange having a spline 16 at its periphery. A rotatable brakemember 17 is provided with an internal spline 18 at its inner peripherywhich meshes and engages the spline 16 so that the rotatable member 17is rotated with the crankshaft 11 but is free to slide axially or float"relative to the shaft 11.

The rotatable member 17 is provided with an annular brake section 19which, when subjected to brake applying pressures at its opposite faces,will effectively restrain movement of the shaft 11. The brake applyingmechanism is composed of an assembly which includes a stationary brakering 20, a movable brake ring 21, and a cover plate 22.

The stationary brake ring 20 is fixed to the machine frame 10 by fourbolts 23 which extend through the feet or lugs 14 and into the frame 10.As may be seen most clearly in FIG. 2, the stationary brake ring 20 hasan axially extending annular projection or rib 24 which is provided witha plurality of radially extending slots 25. The projection 24 has anupper surface 26. The cover plate 22 is secured to the stationary brakering 20 by bolts 27 so that the cover plate 22 is fixed relative to thestationary brake ring 20 and, therefore, the machine frame 10.

The movable brake ring 21 is provided with a plurality of radialprojections 28 which cooperate with the radial slots so that the movablebrake ring 21 is locked or keyed to the stationary brake ring 20, but ismovable within an annular chamber defined by an inner surface 29 of thecover plate 22 and by the stationary brake ring 20. Removable checkplates 280 are bolted to the sides of some or all of the projections 28and are replaceable if worn. in the illustrated embodiment, a total ofeight projections 28 are symmetrically provided around the movable brakering 21, but removable check plates 28a are bolted to the sides ofalternate projections; therefore, only four sets of check plates areprovided.

An annular brake applying pad 30 having a friction material 31 bondedthereto is bolted to the stationary brake ring 20 by bolts 32. Acorresponding annular brake applying pad 33 having a friction material34 bonded thereto is fixed to the movable brake ring 21 by means ofbolts 35. The annular brake section 19 of the rotatable member 17projects between the brake applying pads 30 and 33 and is gripped by thefriction material 31 and 34 when the movable brake ring 21 is urged tothe left as viewed in FIGS. 4, 5, and 6. The movable brake ring 21 is somoved to thereby apply braking forces to the shaft 11 by a plurality ofsprings 36 which are located between the cover plate 22 and the axiallymovable brake ring 21 and which are retained therebetween by a pluralityof recesses 37 provided in the cover plate 22 and a corresponding andcooperating plurality of recesses 38 which are provided in the movablebrake ring 21. Since the rotatable member 17 is free to move axially orfloat relative to the hub 15, it slides axially under the force exertedby the movable brake ring 21 and engages the friction material 31provided on the stationary brake ring 20. It should be noted that whenthe friction members 31 and 34 securely grip the annular brake section19, the braking torque is transmitted to the machine fame 10 through thestationary brake ring 20 directly and through the radial projections 28to the stationary brake ring 20.

The springs 36 are aligned with the braking surface so that their forcesintersect and are uniformly distributed along the annular brake section19 of the rotatable member 17. This minimizes bending moments on themovable brake ring 21, and ensures an even distribution of the brakingforce.

Means are provided to air cool the annular brake section 19 uponapplication of the friction members 31 and 34. To this end, there areprovided a plurality of radial passageways 40 through the annularprojection 24 and into the annular brake chamber formed by thestationary brake ring 20 and the movable brake ring 21.

In order to release the brake, a fluid motor means, which in theillustrated embodiment is an air cylinder means, is provided to cancelor overcome the thrust of the springs 36 and the force applied by themovable brake ring 21 so that the shaft 11 is free to rotate. To thisend, there is provided an annular piston chamber or groove 41 in thestationary brake ring 20 within which an annular piston 42 is slidablymounted for axial movement relative to the stationary brake ring 20.Packing rings 43 and 44 are respectively provided in a groove 45 cut inthe piston 42 and in a groove 46 provided in a sidewall of the annularchamber 41. One end of the annular chamber 41 is closed by an annularring 47 which is fixed to the stationary brake ring 20 by bolts 48 andwhich is fixed to the stationary brake ring 20 and the machine frame 10by the bolts 23 (FIG. 5). Seals 49 are provided between the annular ringand the stationary brake ring 20. A fluid passageway 50 through thestationary brake ring 20 connects the chamber 41 to a source of fluidpressure (not shown).

When the fluid pressure is admitted through the passageway 50 and behindthe annular piston 42, a plurality of brake releasing pins 51 are drivenaxially away from the chamber 41. The brake releasing pins 51 areslidably mounted in bores 52 which extend from the chamber 41 to eachradially extending slot 25 in the annular projection 24. When fluidpressure is applied in this manner, the brake releasing pins 51 bearagainst pressure pads 53 which are bolted to each radial projection 28by bolts 54 to thereby move the movable brake ring 21 against the biasof the springs 36 and, therefore, disengage the friction material 34from the annular brake section 19.

When fluid pressure behind the piston 42 is released, the springs 36force the movable brake ring 21 back into engagement with the annularbrake section 19, thus setting the brake. The introduction of the fluidfrom behind the piston 42 is usually controlled by foot pedal means (notshown) actuated by the operator.

As may be seen in the drawings, the zones of application of the brakereleasing pins to the ring 21 are closely spaced relative to the zonesof application of the springs 36 to the ring 21 to minimize deflectionof the ring 21.

The brake shown and described herein is illustrated in its originalcondition with no wear between the annular brake section 19 and thefriction members 31 and 34. As the friction members are repeatedlyapplied to the annular brake section,

- however, they are worn, with a consequent reduction in their and themovable brake ring 21 when the brake ring is appliedto the annular brakesection 19. Such an adjustment is accomplished by providing a pluralityof shims 60 between the cover plate 22 and the faces 26 of thestationary brake ring 20. Removal of one or more of the shims 60 willreestablish the original spacing between the cover plate 22 and themovable brake ring 21, thus returning the brake applying spring force toits original value. This operation may be performed, for example, byproviding a gauge having a thickness corresponding to the initialspacing between the cover plate 22 and the movable brake ring 21 whenthe movable brake ring 21 is applied to the annular brake section 19.Periodically, the gauge may be inserted between the radial projections28 and the cover plate 22 through the radial slot 25 and, if clearanceexists, one or more shims may be removed to reestablish thepredetermined spacing.

It should be noted that as the shims 60 are removed, the pressure pad 53on each radial projection 28 is drawn closer to the bottom face of eachradial slot 25. To prevent the pressure pad from bottoming on this face,thus preventing brake applying contact between the friction members 31and 34 and the annular brake section 19, means are provided to returnthe pressure pad to its illustrated position spaced from the bottom faceof the radial slot 25. To this end there are provided a plurality ofshims 61 between each pressure pad 53 and its radial projection 28. Theshims 61 are removed on a one-for-one basis with the shims by removingthe bolts 54.

Although one preferred embodiment of this invention is illustrated, itis to be understood that various modifications and rearrangements ofparts may be resorted to without departing from the scope of theinvention disclosed.

I claim:

1. A brake for a shaft mounted on a frame and projecting therefromcomprising a rotatable member mounted on said projecting shaft forrotation therewith having an annular brake section, a stationary brakering mounted on said frame between said frame and said brake memberhaving a face adjacent to one side of said annular brake section, anaxially movable brake ring adjacent to the other side of said annularbrake section remote from said frame, locking means between saidstationary brake ring and said axially movable brake ring to preventrelative rotation therebetween, a cover plate fixed to said stationarybrake ring and, with said stationary brake ring, defining an annularchamber within which said annular brake section and said axially movablebrake ring are located, spring means having one end thereof abutting aportion of said cover plate which is nonadjustable relative to theremaining portion of said cover plate, the other end of said springmeans extending within said annular chamber and coacting between saidcover plate and said axially movable brake ring to bias said brake ringagainst the shaft annular brake section, means to increase the biasingforce of said spring means to compensate for any wear between brakerings and said annular brake section, said means comprising means toadjust the cover plate, including said nonadjustable portion of saidcover plate and said remaining portion of said cover plate, to any oneof a number of fixed positions relative to said stationary brake ring,whereby the distance between said nonadjustable portion of said coverplate and said stationary brake ring may be varied to thereby vary thebiasing force of said spring means, and fluid motor means adapted toovercome the bias of said spring means to thereby release the brake.

2. A brake according to claim 1 wherein said stationary brake ring isprovided with radial slots and said movable brake ring is provided withradial projections which cooperate with said slots to comprise saidlocking means.

3. A brake according to claim 2 wherein at least some of said radialprojections are provided with replaceable side check plates which areengageable with said radial slots.

4. A brake according to claim I wherein the forces of said springsintersect portions of said annular brake section to thereby eliminatebrake applying bending forces applied to said movable brake ring.

5. A brake according to claim 1 wherein said means to increase thebiasing force of said spring means comprises shim means between saidcover plate and said stationary brake ring to space said cover plate andsaid movable brake ring a predetermined distance apart when said movablebrake ring is biased against said annular brake section whereby removalof said shim means decreases said predetermined distance between saidcover plate and the movable brake ring and the spacing between the coverplate and the stationary brake ring to increase the biasing force ofsaid spring means.

6. A brake according to claim 1 wherein said fluid motor means comprisescylinder means within said stationary brake ring, piston means slidablewithin said cylinder means, and brake releasing pin means extendingbetween said piston means and said movable brake ring, wherebyapplication of fluid pressure behind said piston moves said movablebrake ring away from said annular brake section to thereby release thebrake.

7. A brake according to claim 6 wherein said cylinder means comprises anannular groove in said stationary brake ring and said piston meanscomprises a flat ring axially slidable within said groove.

8. A brake according to claim 1 wherein cooling means are provided forsaid brake.

9. A brake according to claim 8 wherein said cooling means comprises aplurality of radially extending passageways through said stationarybrake ring and opening into said annular chamber.

10. A brake for a shaft mounted on a frame and projecting therefromcomprising a rotatable brake member mounted on said projecting shaft forrotation therewith having an annular brake section, a stationary brakering mounted on said frame between said frame and brake member having aface adjacent to one side of said annular section, an axially movablebrake ring adjacent to the other side of said annular section remotefrom said frame, locking means between said stationary ring and saidaxially movable brake ring to prevent relative rotation therebetween, acover plate fixed to said stationary brake ring and, with saidstationary brake ring, defining an annular chamber within which saidannular brake section and said axially movable brake ring are located,spring means between said cover plate and said axially movable brakering to bias said brake ring against said annular brake section and tothereby apply the brake to the shaft, means to increase the biasingforce of said spring means to its original force to compensate for anywear between said movable brake ring and said annular brake section,said means to increase said force comprising shim means between saidcover plate and said stationary brake ring, whereby removal of said shimmeans decreases the spacing between said cover plate and said stationarybrake ring and thereby increases the biasing force of said spring means,fluid motor means comprising cylinder means within said stationary brakering, piston means slidable within said cylinder means, brake releasingpin means extending between said piston means and said movable brakering whereby application of fluid pressure behind said piston meansmoves said movable brake ring away from said annular brake section, andshim means between said brake releasing pin means and said movable brakering.

11. A brake according to claim 10 wherein said stationary brake ring isprovided with radial slots and said movable brake ring is provided withradial projections which cooperate with said slots to comprise saidlocking means.

12. A brake according to claim 11 wherein at least some of said radialprojections are provided with replaceable side check plates which areengageable with said radial slots.

13. A brake according to claim 10 wherein said rotatable brake member isaxially movable with respect to said projecting shaft.

M. A brake according to claim 10 wherein said cylinder means comprisesan annular groove in said stationary brake ring and said piston meanscomprises a flat ring axially slidable within said groove.

15. A brake according to claim 10 wherein cooling means are provided forsaid brake.

16. A brake according to claim wherein said cooling means comprises aplurality of radially extending passageways through said stationarybrake ring and opening into said annular chamber.

17. A brake for a shaft mounted on a frame and projecting therefromcomprising a rotatable brake member mounted on said projecting shaft forrotation therewith and for axial movement with respect to said shaft,said brake member having an annular brake section, a stationary brakering mounted on said frame between said frame and said brake memberhaving a face adjacent to one side of said annular section, an axiallymovable brake ring adjacent to the other side of said annular sectionremote from said frame, locking means between said stationary brake ringand said axially movable brake ring to prevent relative rotationtherebetween, a cover plate fixed to said stationary brake ring and,with said stationary brake ring defining an annular chamber within whichsaid annular brake section and said axially movable brake ring arelocated, spring means between said cover plate and said axially movablebrake ring to bias said axially movable brake ring against said annularbrake section and to thereby apply the brake to the shaft, said annularchamber having an axial dimension which is sufficient to establishclearance between said cover plate and said movable brake ring when saidannular brake section is engaged by said movable brake ring, saidclearance defining the brake release and brake application stroke ofsaid axially movable brake ring, said stroke being increased by wearbetween said stationary brake ring and said annular brake section andbetween said annular brake section and said axially movable brake ringwith a corresponding decrease in the biasing force exerted by saidspring means, means to reestablish said biasing force and to reduce saidstroke to its initial extent comprising removable shim means betweensaid cover plate and said stationary brake ring.

18. A brake according to claim 17 wherein fluid motor means is providedto overcome the bias of said spring means to thereby release the brake.

19. A brake according to claim 18 wherein said fluid motor meanscomprises cylinder means within said stationary brake ring, piston meansslidable within said cylinder means, and brake releasing pin meansextending between said piston means and said movable brake ring, wherebyapplication of fluid pressure behind said piston moves said movablebrake ring away from said annular brake section to thereby release saidbrake.

20. A brake according to claim 19 wherein said cylinder comprises anannular groove in said stationary brake ring and said piston meanscomprises a flat ring axially slidable within said groove.

21. A brake according to claim 17 wherein said stationary brake ring isprovided with radial slots and said movable brake ring is provided withradial projections which cooperate with said slots to comprise saidlocking means.

22. A brake according to claim 21 wherein at least some of said radialprojections are provided with replaceable side check plates which areengageable with said radial slots.

23. A brake according to claim 17 wherein cooling means are provided forsaid brake.

therefrom com rising a rotatable member mounted on said pro ecting shatfor rotation therewith having an annular brake section, a stationarybrake ring mounted on said frame between said frame and said brakemember having a face adjacent to one side of said annular brake section,an axially movable brake ring adjacent to the other side of said annularbrake section remote from said frame, locking means between saidstationary brake ring and said axially movable brake ring to preventrelative rotation therebetween, a cover plate fixed to said stationarybrake ring and, with said stationary brake ring, defining an annularchamber within which said annular brake section and said axially movablebrake ring are located, spring means between said cover plate and saidaxially movable brake ring to bias said brake ring against the annularbrake section, means to increase the biasing force of said spring meansto compensate for any wear between said brake rings and said annularbrake section, said means to increase the biasing force comprising shimmeans between said cover plate and said stationary brake ring to spacesaid cover plate and said movable brake ring a predetermined distanceapart when said movable brake ring is biased against said annular brakesection whereby removal of said shim means decreases said predetermineddistance between said cover plate and the movable brake ring and thespacing between the cover plate and the stationary brake ring toincrease the biasing force of said spring means and fluid motor meansadapted to overcome the bias of said spring means to thereby release thebrake.

26. A brake for a shaft mounted on a frame and projecting therefromcomprising a rotatable member mounting on said projecting shaft forrotation therewith having an annular brake section, a stationary brakering mounted on said frame between said frame and said brake memberhaving a face adjacent to one side of said annular brake section, anaxially movable brake ring adjacent to the other side of said annularbrake section remote from said frame, locking means between saidstationary brake ring and said axially movable brake ring to preventrelative rotation therebetween, a cover plate fixed to said stationarybrake ring and, with said stationary brake ring defining an annularchamber within which said annular brake section and said axially movablebrake ring are located, spring means having one end thereof abutting aportion of the cover plate which is nonadjustable relative to theremaining portion of the cover plate, the other end of said spring meansextending within said annular chamber and coacting between said coverplate and said axially movable brake ring to bias said brake ringagainst the annular brake section, said means to increase the biasingforce comprising shim means between said cover plate and said stationarybrake ring to space said cover plate and said movable brake ring apredetennined distance apart when said movable brake ring is biasedagainst said annular brake section, whereby removal of said shim meansdecreases said predetermined distance between said cover plate and themovable brake ring and the spacing between the cover plate and thestationary brake ring to increase the biasing force of said springmeans, and fluid motor means adapted to overcome the bias of said springmeans to thereby release the brake.

1. A brake for a shaft mounted on a frame and projecting therefromcomprising a rotatable member mounted on said projecting shaft forrotation therewith having an annular brake section, a stationary brakering mounted on said frame between said frame and said brake memberhaving a face adjacent to one side of said annular brake section, anaxially movable brake ring adjacent to the other side of said annularbrake section remote from said frame, locking means between saidstationary brake ring and said axially movable brake ring to preventrelative rotation therebetween, a cover plate fixed to said stationarybrake ring and, with said stationary brake ring, defining an annularchamber within which said annular brake section and said axially movablebrake ring are located, spring means having one end thereof abutting aportion of said cover plate which is nonadjustable relative to theremaining portion of said cover plate, the other end of said springmeans extending within said annular chamber and coacting between saidcover plate and said axially movable brake ring to bias said brake ringagainst the shaft annular brake section, means to increase the biasingforce of said spring means to compensate for any wear between brakerings and said annular brake section, said means comprising means toadjust the cover plate, including said nonadjustable portion of saidcover plate and said remaining portion of said cover plate, to any oneof a number of fixed positions relative to said stationary brake ring,whereby the distance between said nonadjustable portion of said coverplate and said stationary brake ring may be varied to thereby vary thebiasing force of said spring means, and fluid motor means adapted toovercome the bias of said spring means to thereby release the brake. 2.A brake according to claim 1 wherein said stationary brake ring isprovided with radial slots and said movable brake ring is provided withradial projections which cooperate with said slots to comprise saidlocking means.
 3. A brake according to claim 2 wherein at least some ofsaid radial projections are provided with replaceable side check plateswhich are engageable with said radial slots.
 4. A brake according toclaim 1 wherein the forces of said springs intersect portions of saidannular brake section to thereby eliminate brake applying bending forcesapplied to said movable brake ring.
 5. A brake according to claim 1wherein said means to increase the biasing force of said spring meanscomprises shim means between said cover plate and said stationary brakering to space said cover plate and said movable brake ring apredetermined distance apart when said movable brake ring is biasedagainst said annular brake section whereby removal of said shim meansdecreases said predetermined distance between said cover plate and themovable brake ring and the spacing between the cover plate and thestationary brake ring to increase the biasing force of said springmeans.
 6. A brake according to claim 1 wherein said fluid motor meanscomprises cylinder means within said stationary brake ring, piston meansslidable within said cylinder means, and brake releasing pin meansextending between said piston means and said movable brake ring, wherebyapplication of fluid pressure behind said piston moves said movablebrake ring away from said annular brake section to thereby release thebrake.
 7. A brake according to claim 6 wherein said cylinder meanscomprises an annular groove in said stationary brake ring and saidpiston means comprises a flat ring axially slidable within said groove.8. A brake according to claIm 1 wherein cooling means are provided forsaid brake.
 9. A brake according to claim 8 wherein said cooling meanscomprises a plurality of radially extending passageways through saidstationary brake ring and opening into said annular chamber.
 10. A brakefor a shaft mounted on a frame and projecting therefrom comprising arotatable brake member mounted on said projecting shaft for rotationtherewith having an annular brake section, a stationary brake ringmounted on said frame between said frame and brake member having a faceadjacent to one side of said annular section, an axially movable brakering adjacent to the other side of said annular section remote from saidframe, locking means between said stationary ring and said axiallymovable brake ring to prevent relative rotation therebetween, a coverplate fixed to said stationary brake ring and, with said stationarybrake ring, defining an annular chamber within which said annular brakesection and said axially movable brake ring are located, spring meansbetween said cover plate and said axially movable brake ring to biassaid brake ring against said annular brake section and to thereby applythe brake to the shaft, means to increase the biasing force of saidspring means to its original force to compensate for any wear betweensaid movable brake ring and said annular brake section, said means toincrease said force comprising shim means between said cover plate andsaid stationary brake ring, whereby removal of said shim means decreasesthe spacing between said cover plate and said stationary brake ring andthereby increases the biasing force of said spring means, fluid motormeans comprising cylinder means within said stationary brake ring,piston means slidable within said cylinder means, brake releasing pinmeans extending between said piston means and said movable brake ringwhereby application of fluid pressure behind said piston means movessaid movable brake ring away from said annular brake section, and shimmeans between said brake releasing pin means and said movable brakering.
 11. A brake according to claim 10 wherein said stationary brakering is provided with radial slots and said movable brake ring isprovided with radial projections which cooperate with said slots tocomprise said locking means.
 12. A brake according to claim 11 whereinat least some of said radial projections are provided with replaceableside check plates which are engageable with said radial slots.
 13. Abrake according to claim 10 wherein said rotatable brake member isaxially movable with respect to said projecting shaft.
 14. A brakeaccording to claim 10 wherein said cylinder means comprises an annulargroove in said stationary brake ring and said piston means comprises aflat ring axially slidable within said groove.
 15. A brake according toclaim 10 wherein cooling means are provided for said brake.
 16. A brakeaccording to claim 15 wherein said cooling means comprises a pluralityof radially extending passageways through said stationary brake ring andopening into said annular chamber.
 17. A brake for a shaft mounted on aframe and projecting therefrom comprising a rotatable brake membermounted on said projecting shaft for rotation therewith and for axialmovement with respect to said shaft, said brake member having an annularbrake section, a stationary brake ring mounted on said frame betweensaid frame and said brake member having a face adjacent to one side ofsaid annular section, an axially movable brake ring adjacent to theother side of said annular section remote from said frame, locking meansbetween said stationary brake ring and said axially movable brake ringto prevent relative rotation therebetween, a cover plate fixed to saidstationary brake ring and, with said stationary brake ring defining anannular chamber within which said annular brake section and said axiallymovable brake ring are located, spring means between said cover plateand said axially movable brake ring to biaS said axially movable brakering against said annular brake section and to thereby apply the braketo the shaft, said annular chamber having an axial dimension which issufficient to establish clearance between said cover plate and saidmovable brake ring when said annular brake section is engaged by saidmovable brake ring, said clearance defining the brake release and brakeapplication stroke of said axially movable brake ring, said stroke beingincreased by wear between said stationary brake ring and said annularbrake section and between said annular brake section and said axiallymovable brake ring with a corresponding decrease in the biasing forceexerted by said spring means, means to reestablish said biasing forceand to reduce said stroke to its initial extent comprising removableshim means between said cover plate and said stationary brake ring. 18.A brake according to claim 17 wherein fluid motor means is provided toovercome the bias of said spring means to thereby release the brake. 19.A brake according to claim 18 wherein said fluid motor means comprisescylinder means within said stationary brake ring, piston means slidablewithin said cylinder means, and brake releasing pin means extendingbetween said piston means and said movable brake ring, wherebyapplication of fluid pressure behind said piston moves said movablebrake ring away from said annular brake section to thereby release saidbrake.
 20. A brake according to claim 19 wherein said cylinder comprisesan annular groove in said stationary brake ring and said piston meanscomprises a flat ring axially slidable within said groove.
 21. A brakeaccording to claim 17 wherein said stationary brake ring is providedwith radial slots and said movable brake ring is provided with radialprojections which cooperate with said slots to comprise said lockingmeans.
 22. A brake according to claim 21 wherein at least some of saidradial projections are provided with replaceable side check plates whichare engageable with said radial slots.
 23. A brake according to claim 17wherein cooling means are provided for said brake.
 24. A brake accordingto claim 23 wherein said cooling means comprises a plurality of radiallyextending passageways through said stationary brake ring and openinginto said annular chamber.
 25. A brake for a shaft mounted on a frameand projecting therefrom comprising a rotatable member mounted on saidprojecting shaft for rotation therewith having an annular brake section,a stationary brake ring mounted on said frame between said frame andsaid brake member having a face adjacent to one side of said annularbrake section, an axially movable brake ring adjacent to the other sideof said annular brake section remote from said frame, locking meansbetween said stationary brake ring and said axially movable brake ringto prevent relative rotation therebetween, a cover plate fixed to saidstationary brake ring and, with said stationary brake ring, defining anannular chamber within which said annular brake section and said axiallymovable brake ring are located, spring means between said cover plateand said axially movable brake ring to bias said brake ring against theannular brake section, means to increase the biasing force of saidspring means to compensate for any wear between said brake rings andsaid annular brake section, said means to increase the biasing forcecomprising shim means between said cover plate and said stationary brakering to space said cover plate and said movable brake ring apredetermined distance apart when said movable brake ring is biasedagainst said annular brake section whereby removal of said shim meansdecreases said predetermined distance between said cover plate and themovable brake ring and the spacing between the cover plate and thestationary brake ring to increase the biasing force of said spring meansand fluid motor means adapted to overcome the bias of said spring meansto thereby release the brake.
 26. A brake for a shaft mounted on a frameand projecting therefrom comprising a rotatable member mounting on saidprojecting shaft for rotation therewith having an annular brake section,a stationary brake ring mounted on said frame between said frame andsaid brake member having a face adjacent to one side of said annularbrake section, an axially movable brake ring adjacent to the other sideof said annular brake section remote from said frame, locking meansbetween said stationary brake ring and said axially movable brake ringto prevent relative rotation therebetween, a cover plate fixed to saidstationary brake ring and, with said stationary brake ring defining anannular chamber within which said annular brake section and said axiallymovable brake ring are located, spring means having one end thereofabutting a portion of the cover plate which is nonadjustable relative tothe remaining portion of the cover plate, the other end of said springmeans extending within said annular chamber and coacting between saidcover plate and said axially movable brake ring to bias said brake ringagainst the annular brake section, said means to increase the biasingforce comprising shim means between said cover plate and said stationarybrake ring to space said cover plate and said movable brake ring apredetermined distance apart when said movable brake ring is biasedagainst said annular brake section, whereby removal of said shim meansdecreases said predetermined distance between said cover plate and themovable brake ring and the spacing between the cover plate and thestationary brake ring to increase the biasing force of said springmeans, and fluid motor means adapted to overcome the bias of said springmeans to thereby release the brake.